1. Field of the Invention
The present invention relates to a wireless power transmission system, a wireless power receiving apparatus, and a wireless power receiving method using the wireless power receiving apparatus.
2. Description of the Related Art
Wireless power transmission refers to a technology for wirelessly supplying power to home appliances or electronic vehicles without a conventional wired power line. Via such a wireless power transmission technology, a device requiring power can be wirelessly charged without being connected to a power outlet. Accordingly, relevant research on the wireless power transmission technology is being actively conducted.
The wireless power transmission technology is broadly classified into a magnetic induction method, a magnetic resonance method, and a microwave method. The magnetic induction method is a technology using magnetic inductive coupling between adjacent coils. In this case, a distance between two power transmitting and receiving coils is less than several cm and transmission efficiency is largely changed according to arrangement conditions of the two coils. The magnetic resonance method is a technology for transmitting non-radial magnetic field energy between two resonators spaced apart from each other via resonant coupling. In this regard, it is advantageous that power can be wirelessly transmitted when a distance between transmitting and receiving coils is from 1 m to 2 m, that it is easy to arrange the two coils compared with the magnetic induction method, and that a wireless rechargeable range can be extended using a repeat method. The microwave method is a technology for transmitting power by radiating an electromagnetic wave with an ultra high frequency, such as a microwave, through an antenna. In this case, long-distance wireless power transmission is possible. However, safety issues associated with electromagnetic waves need to be considered.
A wireless power transmission system includes a wireless power transmitting apparatus for wirelessly transmitting power and a wireless power receiving apparatus for wirelessly receiving the power. In this regard, when a plurality of wireless power receiving apparatuses are charged by a single wireless power transmitting apparatus, power received by each wireless power receiving apparatus may vary according to a battery charge state thereof and a relative position or distance from the wireless power transmitting apparatus. Thus, an overvoltage exceeding an allowable voltage of an internal circuit can be applied to the wireless power transmission system, and thus, the internal circuit can break down.
Accordingly, there is a need to control an input state of such overpower in a wireless power receiver.